A tourniquet is a well known device for suppressing hemorrhaging. A bandage twisted tight by an implement such as a stick is traditionally used to apply pressure onto an artery and to therefore stop the flow of blood through a limb.
During emergency situations, when a wounded person experiencing a severe loss of blood is alone, the blood flow can be occluded only if the hemorrhage suppressing force can be self applied. A wound victim, however, is generally physically limited and is not always able to apply the required hemorrhage suppressing force. The actual force needed to suppress hemorrhaging is of course dependent upon the thickness of the limb and upon the depth of the artery within the limb. If the applied force is excessive, bones, for example the fibula and tibia bones located within the leg, are liable to be fractured, and damage to soft tissue, such as late soft tissue complications, is liable to result.
An important consideration for a medic or any other person applying the hemorrhage suppressing force is proper documentation as to the time when the hemorrhage suppressing force was initiated. Ischemia develops in the limb as a result of prolonged arterial occlusion. Physiological and anatomical studies have shown that irreversible muscle damage starts after 3 hours of ischemia and is nearly complete at 6 hours, following occlusion of the artery. As a wound victim suffers the risk of amputation when ischemia develops, it is imperative to indicate the time when the hemorrhage suppressing force was initiated, so that the wound victim can be quickly dispatched to a hospital for treatment and for release of the hemorrhage suppressing force. A wound victim usually does not have the presence of mind to write on the strap the time when the self-applied hemorrhage suppressing force was initiated, and furthermore is generally incapable of applying the required constant hemorrhage suppressing force.
U.S. Pat. No. 7,892,253 discloses a tourniquet for emergency use, and may be applied by using only one hand. The tourniquet comprises an outer sleeve, a buckle connected to one end of the outer sleeve, an inner strap in slidable engagement with the outer sleeve, and a windlass rod connected to the inner strap. The buckle has a raised intermediate bar and a tooth for contacting the outer sleeve. The outer surface of the outer sleeve includes hook and loop structures, in order to detachably interlock first and second portions of the outer surface together while being adjusted to different sized limbs, after the other end of the outer sleeve is passed through the buckle and is secured around the limb. The windlass is rotated to apply a tensile force to the inner strap and a circumferentially applied compression force to the limb for restricting the flow of blood.
Such a tourniquet suffers from several drawbacks. Firstly, the time for feeding the outer sleeve through the buckle and for being secured to the wounded limb is relatively lengthy. Secondly, the tourniquet does not facilitate speedy deployment to trapped limbs. In order to be deployed to trapped limbs, the outer sleeve has to be manually disengaged from the buckle and subsequently passed around the limb and reengaged with the buckle before being tightened. Even a few seconds of delay as a result of this deployment process, in addition to the limited concentration and dexterity of the person attempting to perform a hemorrhage suppressing operation during high stress conditions, particularly the wounded victim during one-handed deployment, can cause fatal blood loss.
Thirdly, there is no control as to the instantaneous hemorrhage suppressing force being applied. The bleeding artery will not be sufficiently occluded if the hemorrhage suppressing force is less than the required magnitude. On the other hand, damage to soft tissue, muscles, nerves and bones within the wounded limb is liable to result, particularly due to the narrow dimension of the strap of approximately 2.5 cm that cuts into the skin, if an excessive force is applied. Due to the pain caused by narrow strap, the wounded victim will tend not to apply a sufficiently high self-applied hemorrhage suppressing force. Thus this prior art tourniquet can be reliably deployed only by an experienced medic or any other medical practitioner.
Moreover, the hook and loop structures needed for adjustment to different sized limbs will not be effectively interlocked in a harsh environment, such as mud and water, and have difficulty to be interlocked during conditions of darkness due to the difficulty in adequately seeing the structures.
Various pneumatic tourniquets are known from the prior art, including GB 713132, US 2013/0245673, TW 201311204 and CN 2875336.
WO 2014/023960 discloses an inflation system for a tourniquet that comprises an unprotected pressurized gas bottle coupled to an inlet port and protruding from the edge of the cuff, a movable piston located between the inlet port and outlet port, and a spring recessed within the chamber that cooperates with the piston to resist backward movement of the piston relative to the inlet port. Disengagement of the piston from the inlet port occurs when the gas pressure in the bottle is greater than a combination of the internal pressure within the bladder and the bias exerted by the spring.
As the gas bottle is unprotected and liable to be damaged, this inflation system is not suitable for use in a battlefield environment. Also, the gas bottle cannot be realistically used for more than one hemorrhage suppression operation since the gas pressure in the bottle is generally significantly greater than the combination of the internal pressure within the bladder and the bias exerted by the spring, and therefore a large majority of the compressed gas will be discharged during the course of a single hemorrhage suppression operation.
It is an object of the present invention to provide a pneumatic tourniquet by which the strap applying a hemorrhage suppressing force is inflatable to a controlled pressure.
It is an additional object of the present invention to provide a pneumatic tourniquet that can be deployed much quicker than prior art devices.
It is an additional object of the present invention to provide a pneumatic tourniquet that can be self-deployed.
It is yet an additional object of the present invention to provide a pneumatic tourniquet that can be reliably deployed in harsh environments such as in mud or water.
It is yet an additional object of the present invention to provide a pneumatic tourniquet having a flow control unit that is completely reusable.
Other objects and advantages of the invention will become apparent as the description proceeds.